This invention relates to a process for installing and stabilizing piles in earth formations. More particularly, the invention is directed to a method for stabilizing and increasing the load bearing capacity, especially with respect to the pull-out resistance or resistance to settlement, of piles, such as those used to support or stabilize offshore structures and drilling platforms. The invention is especially useful in processes in which hollow piles aare embedded in earth formations and stabilized by emplacing and solidifying liquids within radial zones that extend from within the piles out into the surrounding earth formations.
There is frequent need for stationary foundations or pile structures, that will neither yield to the weight of any superstructure placed thereon nor yield to external pull-out forces. The problem of providing such a pile structure becomes especially difficult when it is desired to erect a superstructure above an earth stratum consisting of incompetent earth formations such as loose or sandy earth. Such formations tend to require the driving of very long piles to provide the required load carrying capacity. For example, in the oil industry, serious problems haven arisen in connection with the stabilization of pile structures used to support offshore drilling and production platforms, when such pile structures are embedded in incompetent earth formations on the ocean floor. In addition to the weight of the platform structures per se, the pile structures must be able to withstand the extreme pull-out forces resulting from the constant pounding and overturning forces of water waves and currents against the platform. More recently, such platforms have been subjected to even more violent pull-out forces due to the action of ice-flow in certain arctic regions.
In the ordinary smooth-walled pile an upward axial stress is transmitted to the earth largely or wholly by skin friction. These piles are "driven to refusal," i.e., driven to a depth at which the skin friction and the load-bearing capacity of the formations penetrated becomes sufficient to resist further penetration in response to the driving force. It is also known to form projections or footings on embedded pile structures to act as anchoring means for the piles. Such projections or footings as are known in the prior art consist of metal extensions and the like and are reasonably effective as stabilizers when the pile is embedded in hard earth or stone. However, such a metal projection is of little or no value when the pile structure is embedded in less consolidated earth, such as sandy or loose soil. Thus, the need for a method which will effectively secure a pile structure in incompetent earth formations is apparent. Such a method is provided by the invention.